(1) Field of the Invention
This invention relates to light stabilization of acrylic fibers and polyurethane elastomer fibers. More particularly, it relates to light-stabilized acrylonitrile polymer fibers and polyurethane elastomer fibers, which have incorporated therein a 2-hydroxybenzophenone copolymer as a light stabilizer, and a process for making the light-stabilized acrylonitrile polymer fibers and polyurethane elastomer fibers.
(2) Description of the Related Art
Acrylic fibers, polyurethane elastomer fibers and other organic polymer fibers as used outdoors are exposed to sun light and these fibers as used indoors are exposed to light of a fluorescent lamp. The sun light and the light of a fluorescent lamp include ultraviolet rays having wavelengths of 200 to 400 nm which are baneful to polymeric materials. Ultraviolet rays excite functional groups and/or a residual catalyst, which are present in a polymeric material, to cause a photo-degradation reaction whereby the polymeric material is subject to photo-degradation and color fading.
To protect acrylic fibers and other fibers composed of a polymeric material from photo-degradation and color fading, an ultraviolet absorber is incorporated in the polymeric material to be shaped into fibers. By the incorporation of an ultraviolet absorber, the substantial part of the baneful ultraviolet rays are absorbed, and consequently, the photo-degradation and color fading of the acrylic fibers and other fibers are minimized.
The incorporated ultraviolet absorber should not be volatilized, dissolved or decomposed in the fiber-spinning step or the dyeing step, and should not bleed out to the fiber surface after the fiber is made into textile goods. Acrylic fibers (i.e., acrylonitrile polymer fibers) and polyurethane elastomer fibers are made usually by a wet spinning process wherein a spinning dope of an acrylonitile polymer or polyurethane elastomer in an organic solvent such as dimethylformamide (DMF), dimethylacetamide (DMAc) or dimethylsulfoxide (DMSO) is extruded into a coagulating bath composed of, for example, an aqueous solution of the organic solvent used or a water/methanol mixture and, in the wet-spinning step, a conventional ultraviolet absorber incorporated in the spinning dope is undesirably dissolved into a coagulating bath to a significant extent. Furthermore, when acrylonitrile polymer fibers and polyurethane elastomer fibers are dyed or textile goods thereof are laundered, the incorporated ultraviolet absorber is dissolved into a dyeing bath or a laundering bath to a significant extent. Thus, the light stability of the ultraviolet absorber-incorporated acrylonitrile polymer fibers and polyurethane fibers varies greatly depending upon the solubility of the ultraviolet absorber in a coagulating bath, a dyeing bath and a laundering bath and the compatibility of the ultraviolet absorber in the polymer.
Conventional ultraviolet absorbers include, for example, 2-hydroxybenzophenones such as 2,4-dihydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone and 2-hydroxy-4-octoxybenzophenone, and 2-hydroxyphenylbenzotriazoles such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole and 2-(2'-hydroxy-3',5'-dibutylphenyl)-5-chlorobenzotriazole. These ultraviolet absorbers have the above-mentioned problems. Namely, these ultraviolet absorbers have a molecular weight of about 200 to about 400 and have a poor compatibility with an acrylonitrile polymer and polyurethane and a poor heat resistance, and, during wet spinning, dyeing or laudering, these ultraviolet absorbers are dissolved into a coagulation bath, a dyeing bath or a laundering bath.
In the case of acrylonitrile polymer fibers made of an acrylonitrile copolymer composd of acrylonitrile and a halogen-containing monomer such as vinyl chloride or vinylidene chloride, a larger amount of an ultraviolet absorber must be incorporated therein than in the other polymer fibers to attain the intended light stability, and most ultraviolet absorbers have a poor compatibity with the halogen-containing acrylonitrile copolymer.